Ecological treatment and resource utilization method for lake polluted bottom mud

Abstract

The invention discloses an ecological treatment and resource utilization method for lake polluted bottom mud, and belongs to the technical field of environmental governance and resource recycling. The method comprises the following steps: S1, bottom mud collection and pretreatment; s2, microbial enhanced remediation; s3, phytoremediation synergistic effect; and S4, carrying out post-treatment and recycling on the bottom mud. According to the method, an ecological treatment means is adopted in the whole process, the synergistic effect of microorganisms and plants is utilized, large-scale use of chemical agents is avoided, and the risk of secondary pollution is reduced; through multi-stage treatment of microbial enhanced remediation and phytoremediation, the obvious removal effect on organic pollutants, heavy metals and nutrient substances is achieved; original waste polluted bottom mud is converted into practical products such as building materials and soil amendments, so that the treatment cost of the bottom mud is reduced, and economic added values are created; the process parameters can be flexibly adjusted according to different lake pollution types, degrees and peripheral requirements, and the method is suitable for bottom mud treatment and resource recovery of lakes with various scales and various functions.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental governance and resource recycling, and specifically to an ecological treatment and resource utilization method for polluted lake sediment. Background Technique

[0002] With the acceleration of industrialization and urbanization, a large amount of untreated sewage and waste are discharged into lakes, resulting in serious pollution of lake sediment. These polluted sediments not only contain heavy metals (such as mercury, cadmium, lead, chromium, etc.), organic pollutants (such as polycyclic aromatic hydrocarbons, pesticide residues, petroleum, etc.), but also are rich in nutrients such as nitrogen and phosphorus. If not effectively treated, on the one hand, the polluted sediment will continuously release pollutants into the water body, causing secondary pollution, deteriorating the lake water quality, and affecting the balance and stability of the aquatic ecosystem; on the other hand, it is wasted as a potential resource.

[0003] Traditional sediment treatment methods such as dredging and landfilling occupy a large amount of land resources, and there is still a risk of pollutant leakage during the landfilling process; although chemical solidification can stabilize heavy metals to a certain extent, it has a high cost and may introduce new chemical substances, causing secondary hazards; simple composting treatment is difficult to completely remove organic pollutants and heavy metals, and there are potential safety hazards for agricultural products when the made fertilizer is used in agricultural production. Summary of the Invention

[0004] The purpose of the present invention is to provide an ecological treatment and resource utilization method for polluted lake sediment. The whole process adopts ecological treatment means, utilizes the synergistic effect of microorganisms and plants, avoids the large use of chemical agents, and reduces the risk of secondary pollution; through multi-stage treatment of microbial enhanced remediation and phytoremediation, it has a significant removal effect on organic pollutants, heavy metals and nutrients; the originally abandoned polluted sediment is transformed into practical products such as building materials and soil conditioners, which not only reduces the sediment disposal cost, but also creates economic added value, so as to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solution: An ecological treatment and resource utilization method for polluted lake sediment, including the following steps:

[0006] S1. Sediment collection and pretreatment: Collect polluted lake sediment, and obtain a sediment concentrate with a moisture content of 80%-90% through mechanical screening and sediment-water separation;

[0007] S2. Microbial enhanced remediation: Inoculate a composite microbial agent accounting for 1%-5% of the sediment weight into the sediment concentrate, and perform aerobic fermentation at 25°C - 30°C for 1 - 3 months, and regularly turn the pile during this period;

[0008] S3. Phytoremediation Synergy: Plant pollution-tolerant remediation plants on the sediment after microbial enhanced remediation, with a planting density of 10 - 20 plants per square meter, and harvest the plants after a growth cycle of 6 - 12 months;

[0009] S4. Sediment Post-treatment and Resource Utilization: Mechanically dehydrate the sediment after phytoremediation to a moisture content of 40% - 60%, and add 5% - 15% by weight of binder to make building materials or soil conditioners.

[0010] Preferably, the composite microbial inoculant includes Pseudomonas and Bacillus strains that degrade organic pollutants, and Thiobacillus and yeast strains that have an adsorption and transformation effect on heavy metals.

[0011] Preferably, the pollution-tolerant remediation plants include Phragmites australis, Acorus calamus, and Scirpus validus.

[0012] Preferably, the binder includes cement, lime, and bentonite.

[0013] Preferably, the building materials or soil conditioners are used for the sediment treatment and ecological restoration projects of urban landscape lakes, suburban fishery lakes, and industrial pollution lakes.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] Ecological and Environmentally Friendly: The present invention uses ecological treatment means throughout the process, utilizes the synergy of microorganisms and plants, avoids the large-scale use of chemical agents, reduces the risk of secondary pollution, maximally protects the original biodiversity of the lake ecosystem, and promotes the restoration of ecological balance.

[0016] High-efficiency Purification: Through multi-stage treatment of microbial enhanced remediation and phytoremediation, the present invention has a significant removal effect on organic pollutants, heavy metals, and nutrients, can purify severely polluted sediment to meet various resource utilization standards, and the purification rate can reach more than 80%.

[0017] Diverse Resource Utilization: The present invention transforms the originally waste polluted sediment into practical products such as building materials and soil conditioners, realizes the transformation of resources from "waste" to "treasure", not only reduces the sediment disposal cost, but also creates economic added value, which conforms to the concept of sustainable development.

[0018] Strong Applicability: The present invention can flexibly adjust process parameters according to different lake pollution types, degrees, and surrounding needs, is applicable to the sediment treatment and resource recovery of lakes of various scales and functions, and has a broad application prospect. Brief Description of the Drawings

[0019] Figure 1 It is a flow schematic diagram of the present invention. Detailed Embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Please refer to Figure 1 , the embodiments of the present invention provide an ecological treatment and resource utilization method for polluted lake sediment, including the following steps:

[0022] S1. Sediment collection and pretreatment

[0023] Use professional sampling equipment to collect sediment from the polluted area of the lake. The collection depth is determined according to the pollution degree and sediment characteristics, generally 0.5 - 2 meters. After the collected sediment is mechanically screened to remove large particle impurities (such as stones, branches, etc.), the sediment and water are preliminarily separated by a sediment-water separation device to obtain a sediment concentrate with a water content of 80% - 90%.

[0024] S2. Microbial enhanced remediation

[0025] Inoculate a composite microbial agent into the sediment concentrate. This agent is composed of various microorganisms with specific functions, including Pseudomonas and Bacillus strains that degrade organic pollutants, and Thiobacillus and yeast strains that have adsorption and transformation effects on heavy metals. Inoculate according to 1% - 5% of the sediment weight, stir evenly, and place it in a reaction pool with ventilation and temperature control (25°C - 30°C) for aerobic fermentation for 1 - 3 months. During this period, regularly turn the pile to ensure that the oxygen required for microbial growth and the substrate are in uniform contact. During this process, organic pollutants are gradually decomposed into harmless substances such as carbon dioxide and water, and the forms of heavy metals change through the adsorption, precipitation, oxidation-reduction, etc. of microorganisms, reducing their bioavailability.

[0026] S3. Synergistic effect of phytoremediation

[0027] Plant pollution-tolerant and remediation-functional plants, such as reeds, calamus, and softstem bulrush, on the sediment after microbial enhanced remediation. According to the sediment area and plant growth characteristics, plant them at a reasonable density, generally 10 - 20 plants per square meter. During the growth process of the plants, their roots penetrate deep into the sediment. On the one hand, they absorb the remaining nitrogen, phosphorus and other nutrients to further purify the sediment; on the other hand, substances such as organic acids secreted by the roots can promote the activation and absorption of heavy metals, and some transport proteins in the plants can fix heavy metals in specific tissues, reducing their release into the environment. The plant growth cycle is 6 - 12 months. After the plants mature, they are harvested, and the harvested plants can be subjected to subsequent resource treatment.

[0028] S4, Post-treatment and Resource Utilization of Sediment

[0029] The sediment after phytoremediation is mechanically dehydrated again to reduce the moisture content to 40%-60%. Then, an appropriate amount of binder (such as cement, lime, bentonite, etc., with an addition amount of 5%-15% of the sediment weight) is added, and after stirring and mixing, it is formed into building materials (such as bricks, blocks, etc.) or soil conditioners for landscape gardening. The manufactured building materials need to be cured according to standards, and their strength, durability and other indicators are tested to meet the building requirements; the soil conditioner is formulated according to the needs of different garden plants and used to improve the soil structure and increase fertility.

[0030] A small landscape lake in the central area of a certain city is selected. Due to the long-term influence of surrounding domestic sewage and initial rainwater scouring, the sediment is seriously polluted. A grab sampler is used to evenly collect sediment samples with a depth of 1 meter at the bottom of the lake, with a total amount of about 10 cubic meters. After collection, impurities with a diameter greater than 5 cm are removed through a vibrating screen, and then it is treated with a centrifugal sludge-water separator to obtain about 8 cubic meters of sediment concentrate with a moisture content of about 85%.

[0031] A composite microbial inoculant is prepared. Each strain is obtained from a professional strain preservation institution. After activation and propagation, it is inoculated into the sediment concentrate at a ratio of 3% of the sediment weight, and placed in a reaction tank with an aeration device at the bottom and a sunshade at the top. The volume of the reaction tank is 10 cubic meters, and the temperature is maintained at 28°C through a temperature control system. Aeration is carried out for 8 hours every day, and the pile is turned over every 3 days. The fermentation time is 2 months. During this period, the content changes of organic pollutants (taking polycyclic aromatic hydrocarbons as an example) and heavy metals (taking lead as an example) in the sediment are regularly detected. The content of polycyclic aromatic hydrocarbons drops from the initial 50 mg / kg to 10 mg / kg, and the bioavailable content of lead drops from 20 mg / kg to 5 mg / kg.

[0032] Reeds are planted on the repaired sediment at a density of 15 plants per square meter, and the planting area is about 500 square meters. During the growth period of the reeds, water is applied and weeds are removed in a timely manner to ensure their normal growth. After 6 months, the average plant height of the reeds reaches 1.5 meters. The reeds are harvested, and after testing, the cumulative nitrogen uptake of the above-ground part reaches 20 g / plant, and the cumulative lead uptake is 5 mg / plant.

[0033] The sediment after phytoremediation is dehydrated with a plate and frame filter press to reduce the moisture content to 50%. 10% (weight ratio) of cement is added as a binder, and after stirring evenly, it is poured into a mold to make small landscape bricks. After 28 days of standard curing, the compressive strength of the bricks reaches 10 MPa, meeting the use requirements of non-load-bearing landscape buildings. The remaining sediment is added with an appropriate amount of organic fertilizer to adjust the formula and used as a soil conditioner for the lakeside flower bed. The flowers grow vigorously and the soil fertility lasts.

[0034] For a suburban fishery and aquaculture lake, its bottom sediment is polluted by pesticides and chemical fertilizers carried by the backflow of surrounding farmland. About 20 cubic meters of bottom sediment at a depth of 0.8 meters from the lake bottom was collected by a cutter suction dredger. After removing debris through a grid sieve, it was preliminarily separated into mud and water by a hydrocyclone, and 16 cubic meters of bottom sediment concentrate with a moisture content of 82% was obtained.

[0035] Inoculate the bottom sediment concentrate with 2% by weight of a composite microbial inoculant, the composition of which is the same as that in Example 1. Place it in an open-air pit (the pit wall and bottom are treated with anti-seepage). The area of the pit is 20 square meters and the depth is 1 meter. Using natural ventilation, manually turn the pile regularly, and control the temperature at about 26°C through a sunshade net, and ferment for 3 months. Detection found that the pesticide residue (taking chlorpyrifos as an example) in the bottom sediment decreased from the initial 30 mg / kg to 5 mg / kg, and the content of the active form of phosphorus decreased by 60%.

[0036] Plant Scirpus validus, with a planting density of 12 plants per square meter and an area of 800 square meters. After growing for 9 months, Scirpus validus is harvested. The phosphorus absorption amount of its roots reaches 30 g / plant, and it has an obvious complexing effect on some heavy metals, reducing the toxicity of heavy metals in the bottom sediment.

[0037] Dehydrate the bottom sediment after phytoremediation to a moisture content of 45%, add 8% (by weight) of bentonite as a binder to make a soil conditioner for potted flowers. Through flower planting experiments, the flower roots are developed and the flowering cycle is extended; part of the bottom sediment is backfilled into the shallow water area of the lake, improving the living environment of benthic organisms at the bottom of the lake, and the fishery output increases by 15% in the following year.

[0038] The application scenario of the method of the present invention is extensive, and it can be applied to the bottom sediment treatment and ecological restoration projects around urban landscape lakes, suburban fishery and aquaculture lakes, and industrial pollution lakes. In urban landscape lakes, the soil conditioner made from the treated bottom sediment is used for lakeside green space construction, which not only beautifies the environment but also reduces the cost of purchasing external soil; the building materials are used for lakeside footpaths, small landscape buildings, etc., improving the landscape quality while realizing the local conversion of resources. In suburban fishery and aquaculture lakes, the purified bottom sediment can be partially backfilled into the lake to improve the ecological environment at the bottom of the lake, provide a better habitat environment for fishery production, and promote fishery production increase; the products made from the excess bottom sediment are sold externally to increase economic benefits. For industrial pollution lakes, this method can effectively reduce the pollution load, reduce the threat to the surrounding ecology, and the utilization of the treated bottom sediment products realizes a virtuous cycle from pollution treatment to resource recovery.

[0039] The above schematically describes the present invention and its implementation manners. This description is not restrictive, and what is shown in the drawings is only one of the implementation manners of the present invention. The actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative efforts without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An ecological treatment and resource utilization method for lake polluted sediment, characterized in that: It includes the following steps: S1. Sediment collection and pretreatment: Collect the polluted sediment of the lake, and obtain a sediment concentrate with a moisture content of 80%-90% through mechanical screening and sediment-water separation; S2. Microbial enhanced remediation: Inoculate a composite microbial inoculant accounting for 1%-5% of the sediment weight into the sediment concentrate, and perform aerobic fermentation at 25°C - 30°C for 1 - 3 months, with regular turning during the period; S3. Synergistic effect of phytoremediation: Plant pollution-tolerant remediation plants on the sediment after microbial enhanced remediation, with a planting density of 10 - 20 plants per square meter, and harvest the plants after a growth period of 6 - 12 months; S4. Post-treatment and resource utilization of sediment: Mechanically dehydrate the sediment after phytoremediation to a moisture content of 40%-60%, and add 5%-15% by weight of a binder to make building materials or soil conditioners.

2. The ecological treatment and resource utilization method for lake polluted sediment according to claim 1, characterized in that: The composite microbial inoculant contains Pseudomonas and Bacillus strains that degrade organic pollutants, as well as Thiobacillus and yeast strains that have an adsorption and transformation effect on heavy metals.

3. The ecological treatment and resource utilization method for lake pollution sediment according to claim 1, characterized in that: The pollution-tolerant remediation plants include Phragmites australis, Acorus calamus, and Scirpus validus.

4. The ecological treatment and resource utilization method for lake pollution sediment according to claim 1, characterized in that: The binder includes cement, lime, and bentonite.

5. The ecological treatment and resource utilization method for lake pollution sediment according to claim 1, characterized in that: The building materials or soil conditioners are used for the sediment treatment and ecological restoration projects of urban landscape lakes, suburban fishery culture lakes, and industrial pollution lakes.

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